Electrical discharge apparatus for spectographic analysis and the like



June 2, 1942.

s. ANDERSON ELECTRICAL DISCHARGE APPARATUS FOR SPECTROGRAPHIC ANALYSIS AND THE LIKE Filed July 2, 1941 JOIIAC'QF 5M1? Av 107E006 734:5 dashed/11 16 Ind/ca es amecamca/ Connedz'on/M/f/ec/nbafl Q23 Auk/ m!" $0 7 v z Z Spec/M r; Ga a 7'0 Geo UNDEb 8/05 JJ v 7'0 POTENTIAL 8/0: IbPoruvrm 570g flrwasnsm 8 OF Mos/v.75? .9

, inafter described at length.

I tribution to industry.

Patented 2, 1 942 OFFICE ELECTRICAL DISCHARGE APPARATUS FOR ISggTOGRAPHIC ANALYSIS' AND THE Stanley Anderson, Chic This invention relates to a new and improved electrical discharge apparatus for spectrographic analysis and the like and has for one of its ago, 111., assignor to Crane 00., Chicago, 111., a corporation of Illinois Application July 2, 1941, Serial No. 400,808 5 Claims. (01.176-12) principal objects the provision of a device capable of producing electrical discharges of predetermined intensities and'qualities for purposes here- At the outset, it should be understood that in pectrographic analyses work the electrical discharge constitutes an essential element of the entire operation. If the discharge can be well regulated it is possible to obtain a quantitative, analysis fully as accurate as a chemical analysis and in only a small fraction of the time required forthe making of the chemical analysis. In industrial plants the spectrograph plays an important role in the immediate analysis of production metals. For example, in the casting of metals or other materials it is necessary is have a definite percentage of each constituent or element in the ultimate product, but after metals, for example, are placed the like and melted, the only way of. ascertaining the percentage of each element in the alloy mixture is by an. analysis of some kind.- It is the general current practice that sample melts are alloy and then by promptly them before any I further drawn of the molten making analyses of pouring is done'operations may be halted if the percentage of elements is not correct. While of course a chemical analysis by wet methods may be made, the foundry is thus required to maintain a batch of molten metal in the operating induction furnace, but it is not practical because a chemical analysis necessitates a relatively large to delay fqundrypouring of the melt for such time asrequired tomake ascostis concerned, realizing that such delays In oontradistinction thereto, however, in r the determination of low concentration alloying elements in steel,. for example, a spectrogra'phic analysis may be made within the space of only a few minutes, and as this inspection can be performedas accurately as a chemical analysis, presiding absolute control of the electrical dis- T charge is maintained, it is truly a valuable con- It hasbeen found that this method is capable of analyzing steel and iron reliably for the elements manganese, silicon. molybdenum, chromium, nickel, copperiand-alu minum and many other elements. The precision attained is quivalent to that of routine chemicalanalysis by wet methods.

Other advantages include Ia) improved control of melts due to increase in speed and to extension of analyses to elements impractical to determine by wet'methods; (b) improvements in reliability of routine analyses; and (0) savings in operating costs.

' An important object provide an apparatus for in which the desirable high voltage is generated for an extremely short time interval and is distributed across a series of insulators with the consequent advantage that proper insulation is morereadily obtained than with other prior devices.

Other important objects will become apparent from the disclosure in connection with the following specification, in which the invention in spectrographic analyses a preferred form is described merely for illustrainto induction furnaces or tive purposes.

In the drawing:

ferred electrical circuitemployed.

Fig. 2 is a perspective view of the apparatus using the rotating spark gaps.

the chemical analysis-would be prohibitive insofar her need not be brush or similar lReferring to Fig. 2, the disc has gap pointsi It will be apparent that a plurality of discs Referring to the diagram of Fig. 1, the reference numeral l indicates generally a source of electromotive force preferably direct current, but alternating current is also usable as itis easily -adapted to the apparatus. Resistances 2, 3, 4, 6, 29 and 3! are connected at suitable, locations in the circuitwith the condensers 1, 8 and 9 which may have similar capacities. The condensers have discharge terminal leads la, 8a, 8b, and 9a. Other means may be substituted for the resistances; for example inductances could be used in place of or in combination with some or all of these resistances. The E. M. F. is applied to the three condensers in parallel and taken from them in series which in efl'ect provides that their voltages are added toeach other, The circuit diagrammatically indicates only one gap at each of points II and I2; however, in practice it is convenient. to actually use double gaps as shown in Fig. 2 for each 01' the diagrammatically shown gaps and I 2 in order that the rotating memdevice.

and I1 operating as one unit in position ll acting between the condensers I and 8. The other set or gap points I8 and I9 operate as 'a unit between condensers and 9 in position 12. with any number of gap points could be used and operated on a singleshaft. W Y

of this invention is to Fig. 1 is a diagrammatic illustration of the pre-- connected with the circuit by a densers I, 8 and 9 through resistances 2, 8, l, 6,

29 and 3| and the motor I3 is rotated. When the .condensers 1, 8 and 9 are practically fully charged the gaps II and I2 break down and the condensers are discharged in series and the total E. M. F. is projected through the resistance 2|, the inductance 22, the auxiliary gap 23 and specimen gap 28. The auxiliary gap could be an integral part of the rotating gap instead of a separate element as shown. and in some installations such a construction might be more desirable. Two small samples 24 of the material to be analyzed are afilxed in jigs 28 and 21 and placed in the circuit following the auxiliary gap 23. The specimen spark gap 28 between the two samples 24 does not offer suflicient insulation in itself to prevent the input voltage" from breaking down through it. Therefore the auxiliary gap 23 is provided which in series with the gap 28 will not discharge at the input voltage or less, thus permitting the condensers to become fully I claim:

1. An' apparatus for causing electrical dis-- sistances being individually wired in series and charged. The effective E. M. F. causing the specimen discharge is directly controlled by the input at l. Irrespective of whether the voltage input is increased or decreased the specimen spark voltage will always be roughly three times jointly in parallel, a condenser in series with each of said groups of resistances and so arranged that resistances are on each side of the condensers in at least all but one of the roups, the said condensers having discharge terminals, a rotor intermittently in series with the condenser discharge terminals,.a motor to rotate the said rotor, the said rotor and condenser discharge terminals having gaps therebetween, a resistance and an inductance in the circuit with the first said gap, the said circuit having an auxiliary gap whereby discharge of condenser chargesis prevented until full capacity of the condenser charges is attained.

2. An apparatus causing electrical discharges between samples of an alloy comprising a circuit having a gap, a supply of altemating,electrothe input voltage or, in other words, the input Y voltage is multiplied by the number of condensers used. Any desired number of condensers may be employed.

Inasmuch as the input voltage is only onethird as much as the resultant specimen spark voltage, the potential does not have to be unduly high at I and insulation is therefore not a great problem. In prior devices of this type wherein the specimen spark voltage was the same as the motive force, a plurality of inductances arranged in a plurality of groups, the said groups of inductances being individually wired in series and jointly in parallel with the said supply 'of E. M. F. condensers wired in series with the said groups of inductances whereby the said condensers are charge in parallel by the supply of E. M. F., the said condensers having discharge terminals, a rotor having electrodes thereon, a. motor to rotate the said rotor, the said rotor electrodes and condenser discharge terminals having rotary gaps therebetweenpwhereby the input voltage insulation of these unduly high I potentials constituted an expensive and elaborate undertaking. Now it is possible to obtain a specimen spark voltage within the desired range of 30,000 to 100,000 volts by only putting in a fraction of'that amount. The condensers receive this fractional voltage in parallel and it is discharged in series under full control. Furthermore, transformers and rectifying equipment used in the source of supply need not be as expensive as with the type of circuit where no multiplication of voltage occurs.

As previously stated, either direct or alternating current may be used for charging the apparatus. With direct current no precise timing of the speedof the rotating. gaps is required,

although the maximum speed of rotation is limited by the values used for resistances 2, 3, 4,

6, 28 and 3| and for capacities of condensers I, 8 and 9. With alternating current, as may be obtained directly from a transformer connected to the commercial supply, the motor l3 must be a synchronous motor in order to properly position the rotating gaps correctly'with respect to the wave-form of the impressed voltage.

The electrical discharge of the gap 28 between thetwo samples 24 has proven under actual operation to be very desirable for spectrographic analyses work. The apparatus is not unduly expensive and is economically operated in conjunction with research or actual industrial performance. v a

I am aware that many details of construction may be varied throughout a wide range without departing from the'principles herein described alnzii I, therefore, do not propose limiting the c m s otherwise than as necessitated by the -prior art.

said' condensers are substantially fully charged they discharge in series through the said rotary gaps and through the first said gap, means for preventing said discharge until the condensers are substantially fully charged.

3. An apparatus causing electrical discharges between samples of an alloy comprising a circuit, a supply of alternating electromotive force, the said circuit having a spark gap, a plurality of condensers having discharge terminals intermittently connected in series with the said spark gap, a resistance connected to each side of all but one of said condensers, the said one remaining condenser having a resistance connected to one side, said resistances in turn connected in parallel with the said source or E. M. F., a rotor having electrodes synchronized with the input 4. An apparatus causing electrical discharges I between samples of an alloy comprising a circuit,

-. a supply of alternating electromotive force, the

said circuit having a sparkgap, a plurality oi condensers intermittently connected in series with the said spark gap, an inductance connected to each side of all but one of said-condensers, the said one remaining condenser havmg an inductance connected to one side, said inductances in turn connected in parallel with the source of E. M. F., a rotor having electrodes synchronized with the input E. M. F., a. motor for rotating said rotor centrally of the said condenser discharge terminals, the said electrodes I and terminals having gaps therebetween, whereintermittent discharge in series of the y charged condensers occurs across said spark plug, another inductance, a resistance and the circuit including an auxiliary gap in the circuit with the spark gap.

5. An apparatus for causing electrical discharges between samples of a material to-be' spectrographically analyzed, comprising a circuit having a gap, a supply of electromctive force, a

plurality of resistances arranged in a plurality of groups, the said groups of resistances being individually wired in series and Jointly in parallel,

- densers having discharge terminals,

a said rotor and condenser discharge terminals having rotary gaps therebetween, whereby the said first named gap andthe rotary gaps are condensers are intermittently bridged when the substantially fully charged, means for preventing a discharge of the said condensers until such time as-they are substantially fully charged STANLEY ANDERSON. 

